Flexible Scan Plan for Touch Controller Signal Attenuation

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Solution Overview

Problem

Capacitive touch sensor panels face attenuation of self-capacitance touch signals when interacting with objects that are not fully grounded, leading to reduced detection accuracy in fully-bootstrapped self-capacitance scans.

Innovation Solution

Implementing partially-bootstrapped self-capacitance scans, where some touch nodes are driven and sensed, others are driven but not sensed, and some are grounded, with mutual capacitance measurements used to scale and adjust scanning operations to reduce attenuation, and dynamically switching to fine mutual capacitance scans when ungrounded objects are detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If fully-bootstrapped self-capacitance scans are used, then measurement precision is improved for grounded objects, but detection accuracy deteriorates for ungrounded objects due to signal attenuation

Engineering Contradiction:

Improveself-capacitance measurement precisionVSAvoiddetection accuracy for ungrounded objects

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The system dynamically switches between fully-bootstrapped self-capacitance scan mode and mutual capacitance scan mode based on detected touch conditions. When a touch is detected, the system transitions to mutual capacitance scanning to maintain detection accuracy for ungrounded objects, while using fully-bootstrapped self-capacitance scanning for non-touch conditions to optimize measurement precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the scanning parameter from fully-bootstrapped self-capacitance mode to mutual capacitance mode when ungrounded objects are detected. This parameter change adapts the measurement approach to the grounding condition of the interacting object, preventing signal attenuation issues.

Inventive Principle:

Principle #35Parameter changes

2Speed

If coarse scans are used to detect ungrounded objects, then detection speed is improved, but measurement precision deteriorates

Engineering Contradiction:

Improvescan speedVSAvoidtouch detection precision

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The system performs coarse scans as a preliminary action to quickly detect the presence of ungrounded objects before conducting finer measurements. This preliminary detection phase enables rapid identification of touch events while maintaining the capability for precise measurement when needed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system dynamically adjusts scan resolution based on detection needs. Coarse scans are used for initial detection to maintain speed, while the system transitions to finer mutual capacitance scanning when ungrounded objects are detected, balancing speed and precision adaptively.

Inventive Principle:

Principle #15Dynamics

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances the detection of ungrounded objects by reducing signal attenuation and improving sensitivity, allowing for more accurate touch event recognition with flexible scanning operations.

Implementation Method 1

Touch events can be sensed on the touch sensor panel by detecting changes in the self-capacitance of the conductive plates (touch nodes)

Methodology Applied

Scientific EffectSelf-capacitance: Capacitance

Implementation Method 2

or by detecting changes in mutual capacitance between the conductive plates

Methodology Applied

Scientific EffectMutual capacitance: Capacitance

Implementation Method 3

In some capacitive-type touch sensing systems, fringing electrical fields used to detect touch can extend beyond the surface of the display, and objects approaching near the surface may be detected near the surface without actually touching the surface

Methodology Applied

Scientific EffectFringing electrical fields: Electric Field

Data Source

PatentUS10365773B2Flexible scan plan using coarse mutual capacitance and fully-guarded measurements

Publication Date: 2019.07.30 APPLE INC

AI summary

A touch controller for flexible scanning operation is disclosed. The touch controller can include circuitry configured to perform coarse detection scans, select a fine scan type based on results from the coarse detection scans, and perform a fine scan corresponding to the selected fine scan type. A fine mutual capacitance scan can be performed when conditions corresponding to a poorly grounded or ungrounded object or user are detected based on the coarse detection scans. A fine fully-bootstrapped self-capacitance scan can be performed when conditions corresponding to a well-grounded object or user are detected based on the coarse detection scans. A touch processor can be configured to sense touch events from the fine scan.